1. Field of the Invention
The present invention relates to prosthetic knees in general and, in particular, to a speed-adaptive and patient-adaptive control scheme and system for an external knee prosthesis.
2. Description of the Related Art
Most conventional active knee prostheses are variable torque brakes where joint damping is controlled by a microprocessor as an amputee walks from step to step. Many brake technologies have been employed for knees including pneumatic, hydraulic and magnetorheological.
With most current prosthetic technology, a prosthetist adjusts knee resistances to tune the artificial leg to the amputee so that the knee prosthesis moves naturally at slow, moderate and fast walking speeds. During use, sensors local to the prosthesis are used to detect walking speed. A microprocessor then adjusts knee resistances based on customized values or data previously programmed by the prosthetist for that specific patient only.
Disadvantageously, such a methodology for programming a prosthetic knee is time consuming for both the prosthetist and the patient and has to be repeated for each patient. Moreover, any unforeseen changes in the patient or in the patient's environment are not compensated for by the knee prosthesis after the patient has left the prosthetist's facility. This lack of adaptiveness in the knee system can disrupt normal locomotion and render the pre-programmed knee uncomfortable or even unsafe. In this situation, the patient must return to the prosthetist's facility for the knee prosthesis to be reprogrammed. Again, undesirably this results in additional wastage of time and further adds to the cost.